1. Field of Invention
The present invention relates to an antenna apparatus having an LNA board, particularly relates to an improvement in a grounding spring provided to stabilize to ground an input of the LNA board.
2. Description of the Related Art
Conventionally, there has widely been spread a system, so-to-speak a car navigation system for inducing to guide an advancing path or the like of one's own vehicle for a driver of an automobile. According to the car navigation system, whereas a current position is specified by a speed, a running distance or the like of one's own vehicle, in order to promote positional accuracy, radio wave transmitted from a GPS satellite is received by a GPS antenna and the current position is specified also by positional information acquired from the received radio wave.
Or, in recent years, in the United States or the like, it has been promoted to provide digital radio broadcast or the like by radio wave transmitted from an artificial satellite. Also in a digital radio receiving system for receiving such a digital radio broadcast, an antenna for receiving radio wave transmitted from the satellite is also needed and a so-to-speak satellite radio receiving antenna is used.
The above-described GPS antenna or satellite radio receiving antenna is constituted by an antenna portion and an LNA (Low Noise Amp) portion, normally, attached with an antenna unit at an antenna board and attached with an LNA board formed with an LNA circuit on a rear side of the antenna board and is mounted to a roof or the like of an automobile in a state of containing the boards in a cover member.
Here, with an object for preventing noise or the like from invading, the LNA board is covered with a shield case and attached with a grounding spring to stabilize to ground an input of the LNA circuit. FIG. 6 shows a constitution example of an antenna apparatus of a prior art. An antenna board 101 is attached with an antenna unit 102 on one face thereof and attached with an LNA board 103 on other face thereof and is attached with a shield case 104 to cover the LNA board 103. The LNA board 103 is attached with a grounding spring 105 to achieve to stabilize to ground an input thereof for bringing a front end thereof into contact with an inner face of the shield case 104.
Meanwhile, there is normally used the grounding spring 105 constituted by skewdly folding back a metal piece in a flat plate shape, one end side thereof is brought into contact with the shield case and other end side thereof is soldered to the LNA board 103. At this occasion, a front end 105a of the grounding spring 105 is brought into press contact with the inner face of the shield case 104 by an elastic force and as shown by FIG. 7, a press force is exerted in an arrow mark A direction. Then, a portion thereof soldered to the LNA board 103 is exerted with a force in an arrow mark C direction by constituting a fulcrum by a point B (in a direction of peeling off the grounding spring 105). Therefore, a stress is applied to a portion of the grounding spring 105 bonded to the LNA board 103 to thereby pose a serious problem in view of reliability.